1. Field of the Invention
The present invention relates to a system for treating a composite plastic which fractionates and recovers a useful material from a plastic composite product occupying much of general waste products and a plastic bottle in container and package waste products.
2. Related Art
Plastic products include a product using a composite plastic obtained by combining a multiple layers of plastics having different materials, a product obtained by forming a combination of some kinds of plastics, and the like. Among them, a production amount of the plastic bottle which is light, tough and sanitary is quickly increased. Accordingly, an amount of discarded plastic bottle corresponding to the container and package waste products among the general waste product generated at a large amount is increased year by year. It is necessary to quickly promote to utilize a polyethylene terephthalate (PET) bottle belonging to the plastic bottles conventionally treated as the general waste products for a recycled material, and it is requested to prepare a system for quickly recovering and reproducing the bottles.
As a prior art of the treating system for recovering the recycled material from the plastic bottles, there is a reproducing plant for PET bottles described in xe2x80x9cCurrent Status and Problems of PET Bottle Recyclexe2x80x9d in Environmental Conservation Engineering (pages 19 to 22, vol. 25 in 1996).
The treating system in the reproducing plant at first performs a cleaning of the recovered plastic bottles and a removal of foreign matters such as aluminum caps and the like. Thereafter, in order to facilitate a selection of material from the composite material used for the plastic bottle, the recovered plastic bottles are crushed into a flake shape, the crushed pieces of the plastic bottles are cleaned by a flake cleaner using an alkali cleaning liquid, and the cleaned crushed pieces are selected into two portions comprising matters floating in a specific gravity fluid and sediments therein. Thereafter, in order to select a plastic with a higher purity after a drying process, the crushed pieces from which labels having various colored designs and small specific gravity are removed by using an air force are recovered as the recycled material for preventing the labels from mixing. Only the selected crushed pieces are again cleaned and dried, thereby being recovered as a useful plastic.
In the prior art mentioned above, since a cleaning system of injecting a lot of cleaning water to the plastic is employed for cleaning a dirt and a smell attached to the plastic, a lot of drain is generated from the treating system, so that it is necessary to prepare equipment for treating the drain with taking into consideration a secondary public environmental pollution due to the drain.
Further, there is a problem that the specific gravity selecting process by the specific gravity fluid in accordance with the prior art mentioned above has a bad selecting rate (a bad recovering rate).
Further, there has been known xe2x80x9cMethod of Treating Used Plastic Bottlexe2x80x9d described in Japanese Patent Unexamined Publication No. 1-148517 and xe2x80x9cMethod of Recovering Polyester Resin Reproduced Raw Material From PET Bottlexe2x80x9d described in Japanese Patent Unexamined Publication No. 61-68207.
The former intends to improve a selecting operation and a crushing efficiency by separating the heated and shrunk used plastic bottles into materials and thereafter crushing at each of the materials. The latter is a process of selecting and recovering the crushed pieces at each of the materials by adding a mineral powder material to the crushed pieces of the crushed PET bottle and utilizing a mechanical friction operation.
Both of the treating methods heat the PET bottles so as to facilitate a separation of the material from the bottles, and since the former separating method manually separates the materials, there is a problem that too many hands are required for treating a lot of plastic bottles. Further, since the latter removes the mineral powder materials attached to the selected crushed pieces, a process of cleaning the selected plastics, a process of recovering the mineral powder materials and the like are required, so that a cost for equipment is increased.
An object of the present invention is to provide a plastic treating system for selecting and recovering high quality plastics at each of materials in order to utilize used plastic bottles as a recycled material.
Another object of the present invention is to recover a high quality plastic.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided a plastic treating system comprising a crushing apparatus for crushing a composite plastic mainly formed by a plastic as a main material, a dry cleaning apparatus for applying a mechanical impact force and frictional force to crushed pieces crushed by the crushing apparatus, and a selecting apparatus for selecting the crushed pieces into various kinds of plastics by utilizing a difference in a specific gravity of the cleaned crushed pieces.
Further, in order to achieve the another object mentioned above, in accordance with the present invention, there is provided a plastic treating method comprising a crushing process of crushing a composite plastic mainly formed by a plastic as a main material, a cleaning process of cleaning crushed pieces crushed in the crushing process, and a selecting process of selecting the crushed pieces into various kinds of plastics by utilizing a difference in a specific gravity of the cleaned crushed pieces, wherein there is further provided a process of cleaning each of the processes at a time of switching the composite plastic material to be treated to another composite plastic being different in both or one of a color and a material.